Rotary fluid pressure device

ABSTRACT

A rotary fluid pressure positive displacement mechanism operative selectively as a fluid pump or motor and including a relatively stationary internally toothed member and a relatively rotary externally toothed rotor having one tooth less than the internally toothed member and in meshing engagement therewith. The rotor partakes of rotary and orbital movement within the internally toothed member with the axis of the rotor describing an orbit around the axis of the internally toothed member. A drive shaft is journalled for rotation on the axis of the internally toothed member and is operatively connected to the rotor.

United States Patent 1191 McDermott [451 Jan. 1,1974

ROTARY FLUID PRESSURE DEVICE Primary Examiner-Carlton R. CroyleAssistant Examiner-John J Vrabllik [76] Inventor: Hugh L. McDermott,6101 Ashcraft I Ave, Minneapolis Minn 55424 Attorney-Ralph F. Merchantet al.

[22] Filed: May 30, 1972 [57] ABSTRACT [21] Appl. No.: 257,915 A rotaryfluid pressure positive displacement mechanism operative selectively asa fluid pump or motor [52] U 8 Cl 418/61 64/9 R 64/31 and including arelatively stationary internally toothed [51] F010 F03c 3/0O member anda relatively rotary externally toothed [58] Fieid "s;; 4l8/61,64/9 R 31rotor having one tooth less than the internally toothed member and inmeshing engagement therewith. The [56] References Cited rotor partakesof rotary and orbital movement within the internally toothed member withthe axis of the UNITED STATES PATENTS rotor describing an orbit aroundthe axis of the inter- Monroe St 3L nauy toothed member A drive haft isjournaned for g g rotation on the axis of the internaliy toothed membere en e a 3,352,247 11/1967 Easton 418/61 and operat'vely connected torotor 4 Claims, 4 Drawing Figures 3 4 Z 423 20 Z/ Z1 1 ROTARY FLUIDPRESSURE DEVICE BACKGROUND OF THE INVENTION Rotary fluid pressuredevices of the type utilizing cooperating internally toothed andexternally toothed members are known, examples of these being found inU. S. Pat. No. 2,821,171, 2,984,215, 2,989,951 and 3,233,524. In thesedevices, a drive shaft is disposed on the axis of the stationary one ofthe toothed members and is eccentric to the rotary toothed member, theaxis of the rotary toothed member describing an orbit about the axis ofthe stationary toothed member. The orbiting and rotating member isconnected to the drive shaft by a connector having an axis oblique tothe axes of the toothed members, and gear teeth at its opposite endshaving generally longitudinally sliding meshing engagement with teeth onthe rotary and orbiting member and on the drive shaft. Due to sizelimitations in devices of the type exemplified by the above-mentionedpatents, particularly in the root diameters of the external teeth of theexternally toothed members, the central toothed opening in theseexternally toothed rotating and orbital members are quite small as arethe'teeth therein. The small size of the teeth of these members, as wellas the teeth of the connector intermeshing therewith, make thisconnection a weak area of the entire structure, and one wherein unduewear occurs. Early failure of the parts in this area necessitates ratherfrequent disassembly of the device and replacement of the worn or brokenparts. I

SUMMARY OF THE INVENTION An important object of this invention is theprovision of a rotary fluid pressure device having substantially greaterstrength in the parts thereof, for a given overall size, than similardevices heretofore produced.

Another object of this invention is the provision of a rotary fluidpressure device having substantially longer wearing qualities thansimilar devices heretofore produced. I

To these ends, I provide a rotary fluid pressure device including acasing which defines a chamber including an internally toothed memberdefining a peripheral wall of the chamber, an externally toothed. memberhaving one tooth less than the internally toothed member in meshingengagement with the internally toothed member and eccentric thereto, agear shaft rigid with the externally toothed member and extendingaxially therefrom, a drive shaft journalled in the casing on the axis ofthe internally toothed member, and a connector element having enlargedopposite ends. The gear shaft and drive shaft have diametricallyenlarged ends dis posed adjacent the opposite ends of the connectorelement remote from the teeth of the externally toothed member, theconnector element and enlarged shaft ends having interengaging drivesurfaces whereby rotation of one of the gear and drive shafts isimparted to the other thereof.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in side elevation of arotary fluid pressure device containing the improvement of thisinvention, some parts being broken away and some parts being shown insection;

FIGS. 2 and 3 are enlarged transverse sections taken on the lines 2--2and 3--3 respectively of FIG. 1; and

FIG. 4 is a view corresponding to FIG. 1 but showing a modifiedarrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGS. 1-3 a casing,indicated generally at 1, comprises a plurality of casing sections 2, 3,4 and 5, the

casing section 5 providing an end wall 6 for the casing l. The casingsection 2 provides an opposite end wall 7 having therein a port 8. Atone side, the casing section 2 is formed to provide a second port 9, theports 8 and 9 being inlet and outlet ports interchangeably as desired.The casing sections 2-5 are rigidly held together in axial alignment bya plurality of circumferentially spaced machine screws 10.

The casing sections 2, 3 and 4 cooperate to define a rotor chamber,indicated at 11 in FIG. 2, the casing section 3 defining a plurality ofcircumferentially spaced internal teeth 12. In the embodimentillustrated in the drawings, the teeth 12 are seven in number. Anexternally toothed rotor 13 is disposed in the chamber 11, the rotor 13having a plurality of circumferentially spaced teeth 14 that are adaptedto move into and out of meshing engagement with the teeth 12. The teeth14 are one less in number than the teeth-12, and cooperate with theteeth 12 to divide the chamber 11 into chamber sections 15 thatalternately expand and contract as the externally toothed member 13rotates within. the chamber 11. During such rotation of the externallytoothed member or rotor 13, the same partakes of orbital movement, theaxis thereof orbiting about the axis of the internally toothed member orcasing section 3. Commutating valve means, not shown, are containedwithin the casing section 2 for supplying fluid to the expanding chambersections 15 and withdrawing fluid from the contracting chamber sections15 during rotary and orbital movement of the externally toothed rotormember 13. Such valve means are clearly disclosed in one or more of theabove-mentioned U. S. patents and, in and of themselves do not comprisethe instant invention. Hence, in the interest of brevity, detailedshowing and description thereof is omitted.

A drive shaft 16 extends axially outwardlythrough an axial opening 17 inthe end wall 6 of the casing l, in axial alignment with the internallytoothed member or casing section 3. Inwardly of the casing section 5,the drive shaft 16 is formed to provide a diametrically enlargedcylindrical head 18 which includes a cylindrical skirt portion 19, thehead 18, with its skirt 19 being journalled in the casing section 5 bymeans of roller bearings 20. The roller bearings 20 are conventional innature, being supported in outer races 21 and annular cages 22, theraces 21 being held in axially spaced apart relationship by an annularspacer 23.

Means for operatively connecting the externally toothed rotor member 13to the drive shaft 16 comprises a gear shaft 24 and a cooperatingconnector element 25. The externally toothed rotor member 13 is providedwith an axial opening formed to provide cir-- cumferentially spacedspline teeth 26 that mesh with cooperating spline teeth 27 on the gearshaft 24, the gear shaft 24 being preferably press-fitted in the splinedopening of the rotor 13. Although not specifically shown, it may beassumed that one end of the shaft 24 is operatively connected to thevalve mechanism within the casing section 2 to provide proper valvingfor the apparatus.

The gear shaft 24 extends through an opening 28 in the wall or casingsection 4, the opening 28 being coaxial with the internally toothedmember 3 and drive shaft 16, the opening 28 having a diametersufficiently less than the root diameter of the external teeth 14 on themember 13 so that the member 13 covers the opening 28 at all timesduring its orbital and rotary movement in the chamber 11, see FIG. 2.Axially outwardly of the opening 28, the gear shaft 24 includes adiametrically enlarged head 29 that is disposed within the recessdefined by the drive shaft skirt 19. The head 29 is formed to provide anaxial recess having circumferentially spaced internal teeth 30 therein.The teeth 30 have axially sliding meshing engagement with cooperatingteeth 31 at one end of the connector element 25. At its opposite end,the connector element 25 is formed to provide circumferentially spacedexternal teeth 32 similar to the teeth 31, these having meshingengagement with cooperating internal teeth 33 formed within an axialrecess 34 in the enlarged head 18, the teeth 33 being substantiallyidentical to the teeth 30. The offset relationship between the heads 18and 29 disposes the connector element 25 on an axis that is oblique tothe offset parallel axes of the drive shaft 16 and gear shaft 24, asclearly shown in FIG. 1. The gear teeth 30-33 are so shaped that, whenorbital and rotary movement is imparted to the gear shaft 24, or whenrotary movement is imparted to the drive shaft 16, the teeth 31 and 32of the connector element 25 partake of a rocking and axial slidingmovement relative to their respective teeth 30 and 33. By providing agear shaft 24 that is rigidly secured to the externally toothed gear 13,and which shaft has an internally toothed head the inner diameter ofwhich is substantially larger than the splined opening in the externallytoothed gear 13, I am able to provide cooperating teeth 30 and 31 thathave substantially greater thickness and interengaging surface areasthan have been heretofore possible. Further, in view of the tight fitbetween the externally toothed gear member 13 and the gear shaft 24, astronger connection therebetween is had, without wear on the splineteeth 26 and 27.

DETAILED DESCRIPTION OF MODIFIED ARRANGEMENT In the modified form of theinvention illustrated in FIG. 4, an elongated casing 35 is shown ascomprising casing sections 2', 3', 4' and 36, the casing sections 2', 3,and 4' being identical to the casing sections 2, 3 and 4. The casingsection 3 contains an externally toothed gear member 13' identical tothe gear member 13. The casing sections 2', 3', 4' and 36 are securedtogether in end-to-end relationship in the same manner as the casing 1,by machine screws The casing section 36 is formed to provide arelatively larger transverse portion 37 and a relatively smallertransverse or diameter hub portion 38, the hub portion 38 containingroller bearings 39 which journal a drive shaft 40 in axial alignmentwith the internally toothed casing section 3'. The bearings 39 are heldin spaced apart relationship by an annular spacer 41. The

casing section 36 cooperates with the casing section 4' to define anenlarged chamber 42 into which the drive shaft 40 projects. The innerend of the drive shaft 40 is formed to provide an enlarged externallytoothed head 43 within the chamber 42. An annular wear plate 44 isdisposed between the toothed head 43 and the adjacent annular wallsurface of the casing section 36, the annular wall surface beingindicated at 45.

A splined gear shaft 46 is press-fitted in the externally toothed gear13 and projects through an opening 28' in the casing section 4, the gearshaft 46 terminating within the chamber 42 in an enlarged externallytoothed head 47 identical to the toothed head 43 on the drive shaft 40.An annular wear plate 48 is disposed between the toothed head 47 and theadjacent surface of the casing section 4.

As shown, the shafts 40 and 46 are disposed in laterally offset parallelrelationship, in the same manner as the shafts 16 and 24, the toothedheads 43 and 47 being connected by a tubular connector element 49 havinginternal teeth 50 that extend longitudinally thereof and haveintermeshing axial sliding engagement with the external teeth on theheads 43 and 47. The opposite ends of the tubular connector element 49are adapted to slideably engage the wear plates 44 and 48 to limit axialmovement of the connector element 49. The tubular connector element 49operates in the same manner as the connector element 25, the arrangementbeing such that the teeth 43, 47 and 50 have substantially greaterthickness and wearing surface areas than connectors heretofore useddirectly between the drive shaft and externally toothed gear member.

I have found that, with the driving connections shown in both FIGS. 1and 4, a greatly extended useful life is obtained in fluid pressuredevices of the type hereinbefore described. While I have shown anddescribed a commercial embodiment of my improved construction, and asingle modified form thereof, it will be understood that the same iscapable of further modification without departure from the spirit andscope of the invention, as defined in the claims.

What is claimed is:

1. In a rotary fluid pressure device comprising, a casing including aninternally toothed relatively stationary gear, a cooperating externallytoothed gear having at least one less tooth than said internally toothedgear and disposed therein for intermeshing engagement therewith and forrotary and orbital movement wherein the axis of said externally toothedgear describes an orbit around the axis of the internally toothed gear,said externally toothed gear having an axial opening therethrough, and adrive shaft journalled in said casing on the axis of said internallytoothed gear; the improve ment comprising, a gear shaft rigidly mountedin said axial opening and extending axially from said externally toothedgear for rotary and orbital movement in common therewith, an enlargedhead on said gear shaft axially spaced from said externally toothedgear, an enlarged inner head on said drive shaft, and a connectorelement having an axis disposed oblique to the axes of said gear shaftand drive shaft, said enlarged heads and connector element havingintermeshing gear teeth of a diameter substantially greater than thediameter of said axial opening in the externally toothed gear.

2. The rotary fluid pressure device defined in claim 1 in which saidaxial opening defines a plurality of circumferentially spaced splineteeth, said gear shaft having spline teeth interfitting the teeth insaid axial opening, the intermeshing teeth on said heads and connectorelement having substantially greater circumferential and radialmeasurement than said spline teeth.

3. The rotary fluid pressure device defined in claim 2 in which saidenlarged heads on the gear and drive shafts define axial recesses, theteeth of said enlarged heads comprising internal gear teeth in saidrecesses, the teeth on said connector element being external gear teeth.

4. The rotary fluid pressure device defined in claim 2 in which theteeth on said enlarged gear shaft and surface.

1. In a rotary fluid pressure device comprising, a casing including an internally toothed relatively stationary gear, a cooperating externally toothed gear having at least one less tooth than said internally toothed gear and disposed therein for intermeshing engagement therewith and for rotary and orbital movement wherein the axis of said externally toothed gear describes an orbit around the axis of the internally toothed gear, said externally toothed gear having an axial opening therethrough, and a drive shaft journalled in said casing on the axis of said internally toothed gear; the improvement comprising, a gear shaft rigidly mounted in said axial opening and extending axially from said externally toothed gear for rotary and orbital movement in common therewith, an enlarged head on said gear shaft axially spaced from said externally toothed gear, an enlarged inner head on said drive shaft, and a connector element having an axis disposed oblique to the axes of said gear shaft and drive shaft, said enlarged heads and connector element having intermeshing gear teeth of a diameter substantially greater than the diameter of said axial opening in the externally toothed gear.
 2. The rotary fluid pressure device defined in claim 1 in which said axial opening defines a plurality of circumferentially spaced spline teeth, said gear shaft having spline teeth interfitting the teeth in said axial opening, the intermeshing teeth on said heads and connector element having substantially greater circumferential and radial measurement than said spline teeth.
 3. The rotary fluid pressure device defined in claim 2 in which said enlarged heads on the gear and drive shafts define axial recesses, the teeth of said enlarged heads comprising internal gear teeth in said recesses, the teeth on said connector element being external gear teeth.
 4. The rotary fluid pressure device defined in claim 2 in which the teeth on said enlarged gear shaft and drive shaft heads comprise external gear teeth, said connector element comprising a tube having an inner surface, the teeth of said connector element being internal gear teeth defining at least a portion of said inner surface. 